U.S. Pat. No. 3,075,813 issued Jan. 29, 1963 to Adrien VOHL--being the father of the present inventor--discloses a control rod linkage assembly for assisting in the extension or retraction of telescopic sections carried at the outer free end of the snow discharge pipe spout of a snowblower truck. The control rod linkage assembly consists of a number of pivotally interconnected link bars, extending from the base of the main snow discharge spout up to the telescopic parts at the outer end of the main discharge spout. By pivoting the lower link bar, the intermediate link bars are biased to urge the upper link bars to pivot the telescopic spout extensions accordingly.
One drawback of this otherwise efficient patented system, is that, under rough conditions where the snow discharge chute becomes damaged and bent, the control rod linkage assembly progressively becomes more difficult to operate. The reason for this is that, as the snow discharge chute becomes bent following abuse, the pivotal axes of some of the pivotal joints interconnecting the various link arms of the control rod linkage assembly will tilt. Because a simple axial pin is mounted at the pivot joints, this tilting of the link arms means that the axial pins thereof will become offset from their pivotal axles.
U.S. Pat. No. 3,516,713 issued in 1970 to Wagstaff, addresses this problem by providing a universal joint that operates the chute of a forage harvester. Another example of such universal joints for control rod linkages is disclosed in Canadian patent No. 423,567 issued Oct. 31, 1944--here a ball and socket joint. In this latter patent, the joint has an oilless bearing material surface riding in a metal socket.